Michelle Shocked, a controversial singer and born-again Christian, is under fire for her anti-gay tirade during a concert on Sunday night in San Francisco.

Witnesses say she told the crowd at Yoshi's, "When they stop Prop 8 and force priests at gunpoint to marry gays, it will be the downfall of civilization, and Jesus will come back," and "You can go on Twitter and say, 'Michelle Shocked says God hates (anti-gay slur).' " The staff at the venue finally turned off the stage lights and pulled the plug on her performance.

"It was a very painful experience to go through," show guest Matt Penfield told Yahoo! Music. "To be that close to someone who is clearly having a breakdown of some sort is not an emotionally comfortable place to be. I'm still a little bit shaken up. And I don't like to see people vilified. I still love her music and I'm not going to delete her from my playlist or go smash CDs. But if she has made a conscious decision that she is going to use the stage to espouse beliefs that are hateful and damage groups of people, she probably should not be charging money for a concert. If she wants to sit on a panel at a conference or go to a religious festival, I think in that context she should say whatever she wants. But I do think that doing it as a bait-and-switch at a concert performance is really unfair and not showing respect to people."

The Twittersphere reacted to Shocked's show, and so did the promoters of SPACE in Evanston, Ill., where she was set to perform on May 5. They posted this on their official Facebook page:

"Many of you have reached out already following an ugly rant given by Michelle Shocked at her show in San Francisco last night. After speaking with the promoter of that show about the nature of the remarks, it's clear that this is no longer a show we're willing to put our name on. The May 5th performance at SPACE has been cancelled and refunds will be issued at point of purchase."

UPDATE: LGBT activist John Becker has created a petition on Change.org demanding Shocked be held responsible for her hate speech and urging more than a dozen venues to cancel her upcoming shows. So far, nine venues have canceled. Telluride Blues Festival and the Harmony Bar in Wisconsin have yet to respond. So far, 1,450 people have signed the petition about Shocked, who has toured with the all-women's music festival, Lilith Fair.

"Freedom of speech and artistic expression are critically important, but this isn't free speech," says Becker in a statement. "This is hate speech. And in a world where LGBT people are bullied from the pulpit, on the playground, and at the polls, anti-gay hate speech can have serious consequences including legitimizing bullying and hate crimes, and increasing victims' risk of anxiety, depression, and suicide."